Printing process and apparatus



Sept. 7, 1943. w. (3. R085 2,328,586

PRINTING PROCESS AND APPARATUS Filed Feb. 12, 1942 3 Sheets-Sheet 1 I j& Q

INVEN+EIRI William C. Ross Sept. 7, 1943. w. c oss 2,328,586

PRINTING PROCESS AND APPARATUS Filed Feb. 12, 1942 3 Sheets-Sheet 2 I lI I I l Q w *URZQI) William C. Ross INVEN+E1RI I William C. Ross@3015... Q.

5 Sheets-Sheet 5 Filed Feb. 12, 1942 W C ROSS PRINTING PROCESS ANDAPPARATUS Sept. 7, 1943.

paper Patented Sept. 7, 1943 2,328,586 PRINTING PROCESS AND APPARATUSWilliam 0. Ross, Winchester, Mass, assignor to Dewey and Almy ChemicalCompany, North Cambridge, Mass, a corporation of MassachusettsApplication February 12, 1942, Serial No. 430,646 9 Claims. (Cl. 101417) In textile printing, some dye or color is driven completely throughthe interstices of the cloth and reaches the backing surface. Inprinting on a perfecting press, the wet ink of the printing applied tothe first side of the sheet runs against the draw sheet of the secondimpression cylinder. Some of this is picked up by the draw sheet and isoffset on to the printed sheet again, thus producing the printing faultknown as "second-side offset. Whatever ink or color reaches the surfacewhich backs up the type, plate cylinder or roll, I describe as excesscolor. Excess color causes the same fundamental trouble whether textilematerial or paper stock is being printed. If the impression surfacebecomes dirtied with ink, some color will offset from the-impressionsurface to the back of the sheet To prevent this, back grays are used intextile printing and smut rolls in web letter-press work. The functionof both is to absorb the excess color and carry it away before it canstrike through to the blanket or the draw sheet. Smut rolls complicaterotary press work to such an extent and increase the cost of printing tosuch a degree that they are used only as a last resort and on web of thesmut roll and are still commonly used, but, nevertheless, increase thecost of the calico process materially.

In web letter printing, no solution for a dirty draw sheet exists whichavoids a smut roll and still prevents secondside offset from the drawsheet. Only expedients such as "skinning the ink, sand paper drawsheets, and stopping and washing-up the press are used to minimize theoccurrence of offset on the second side. In textile printing, washblankets and continuous blanket washers make printing without back greyspossible.

But the recent appearance of resin bondedcolors which replace the dyespreviously used has driven the textile printing industry back to the use01' back grays. These colors, as contrasted with the direct vat or basicdyes previously used, do not use a bodier such as deatrine or Britishgum which is subsequently washed out, but are composed of water-bearing,pulp color suspended in a solvent solution of a thermo-setting resin.The color, therefore, is in suspension in a resin solution whichcontains water as the internal phase of the emulsion. The water inemulsion behaves in its characteristic water-in-oil manner and stifi'ensthe mass into a thick, but workable paste. Bonding of the color to thefiber, upon printing, is no longer a. phenomenon of adsorption ormordanting, but comes about by "advancing" the liquid resin whichsurrounds the individual textile fibers to an insoluble stage.

Once on the blanket, the emulsion immediately breaks. Theresin-in-solvent is not re-emulsified and cannot be removed by presentblanket washers. The resin solvents soften and destroy the rubberimpregnation of the blanket, and the resin cures in the dryers to a hardand brittle skin.

I have discovered that if the blanket, or draw sheet is coated with anink or color impermeable coating which is applied immediately beforeprinting, and if the coating together with the ink or color is strippedfrom th impression surface after printing and a fresh coating applied,not only may incompatible inks be run against blankets or draw sheetswhich otherwise would be ruined, but a continuously clean, fresh surfaceis maintained on the impression cylinder which, since it never carriesink as it enters the bite, cannot lay color off on the back of the goodsor produce second-side offset. Accordingly, I app y to the supportingsurface (impression surface), whether it be a flexible blanket, tympanor draw sheet, a temporary continuous coating which receives the surplusink, and which is removed periodically and immediately terial which canbe form to the supporting surface, will dry or harden quickly, will formthat surplus ink will not penetrate to the supporting surface and can beremoved easily after printing has taken place. The particular compoundsemployed are described more fully hereinafter,

Of the numerou adaptations of my process necessary to fit it intoexisting press installations, I shall describe the process as adaptedfor textile printing on the wash blanket apparatus as described in theapplication of McMordie et 9.1., Serial No, 404,209, filed July 26,1941, but I i tend no limitation thereby, for it is obvious that theprocessmay be generally used wherever it is desired to maintain a cleanimpression surface.

The McMordie et a1. apparatus is modified only by the addition ofmechanism which applies a fresh, continuous coating to the diately afterthe previous-coating which has been stained by the surplus ink has beenremoved.

In the drawings,

Figure 1 shows a side elevation of an entire a continuous surface soblanket immetextile printing apparatus of the type-described and showsthe general location and arrangement of apparatus here necessary forcarrying out my invention;

Figure 2 is a sectional view of my apparatus on the line 2-2 of Figure1;

Figure 3 is a small perspective view of a portion of the blanket afterpassing under the applicator roll;

Figure 4 is a perspective view of a small portion of the blanket afterthe coating process is complete;

Figure 5 is a side elevation of the apparatus; and

Figure 6 is a sectional view through the apparatus on the line 6, 6 ofFigure 2.

In the McMordie et a1. device, which is shown in Figure 1, the blanketIU' loops around the impression cylinder II and, crossing the guide rollI2, loops through a preliminary washer or muddler 13. Here, inconventional printing, using gum-thickened color, some of the color isremoved and the remainder broken up by a counter-running brush I4. Thebristles of this brush not only scour the blanket but also act as a pumpto raise water from the supply pan and flood the outrunning surface ofthe blanket with water which is maintained on the blanket surface by thetroughlike form given to it by the blanket guides 15. With gum colors,soaking on the outward run softens the color so much that it is removedcompletely in a single pass through the washer and squeeze dryer l6.

The mechanism for applying the coating material to the blanket I0 issupported from two 2 bar extensions ll-l8 of the main frame member ofthe dryer [9 by means of two sub-frames 2 l-22 bolted to the 2 bars. Thesub-frames are provided with ways 23-24 in which supporting blocks 25-26may slide vertically. The supporting blocks rest on arms 21-28 which arepivoted at 29-3l, the position of which may be adjusted vertically bymeans of the screws 32-33 which are threaded through the lugs 34-35 onthe subframe. The stop screws 36-31 allow the arm to be locked rigidlyin position when vertical adjustment has been secured.

The applicator roll 33 is journaled on pillow blocks 39-41 which arebolted to the supporting blocks 25-26. This is driven at blanket speedand receives its power from a chain 42 led off, as Figure 1 shows, to alive axle of the blanket reversing roll 43. The applicator roll ispreferably equipped with a bronze or copper sleeve 44 which bears anall-over engraved pattern of small depressions 45 and, in fact, is quitesimilar to an all-over textile print roll.

The coating composition, in the form of a plastic but freely movableslurry, is brought up to the applicator roll by the furnisher brush 46which revolves on journals mounted on the ends of the slurry pan 41.This is not a driven brush but revolves only because of friction betweenit and the applicator roll. roll by the furnisher brush is scraped offby the doctor blade 48 which is preferably a stiff strip of laminatedresin. This is held in the vise blocks 49-5l and is adjusted for bearingagainst the roll by the screws 52-53 which are threaded through lugs onthe doctor blade support arms 54-55. The tubular spreader bar 56 issupported on threaded standards 51-58 which pass through the slottedbrackets 59-6I attached to the sub-frames. It may be adjusted to bearagainst the surface of the blanket.

Excess material applied to the A free running rubber covered roll 62 isjournaled on brackets 63-64 mounted on the main frame above theapplicator. Its function is merely that of a backing roller and servesto keep pressure on the applicator roll.

In operation, slurry is put into the slurry storage tank 65 and iscontinuously fed to the slurry pan of the coater by the gear pump 66.All excess runs back through the drain 61 to the tank. The coating firstappears on the blanket as a series of small dots or daubs 68 (Figure 3)because the coating is picked out of the depressions 45 of theapplicator roll as the blanket l0 passes over the roll. These daubs aresmoothed to an even, continuous film 69 (Figure 4) by the spreader bar56.

On its inward run, the blanket turns at right angles over the guide rollH and enters the dryer 19, which is usually reversed on itself toconserve floor space, and made up of an inrunning tunnel l2 and anoutrunning tunnel 13. Air, heated by steam coils in the fan house 14,circulates through both tunnels. The blanket enters the lower tunnel 12of the dryer l9, and, in passing through the tunnel, the coating isdried or hardened. In the case of a water base coating, all water isevaporated from the coating which dries to a smooth, ink impenetrableand solvent impervious film. Despite its dryness, it remains flexibleand coherent and withstands doubling about the reversing rolls of thedryer and the guide rolls of the apparatus without cracking or peelingoff.

As the coated blanket passes the printing mechanism, here indicatedconventionally as an impression cylinder l l, the textile l5, engravedcolor rolls 16, furnisher brushes TI, and color pans 18, the coatingpicks up charges of the various colors which are driven through thetextile. The blanket then passes through muddling apparatus l3(Figure 1) where some of the soft color is picked off on the surface ofthe reversing roll 19 and the blanket is then wet scrubbed by thecounter-running brush M. The blanket travels to the rear of the machinewhile it is submerged beneath a sheet of water onthe top surface of theblanket, this water having been lifted up on to the blanket by the brushl4. During the time that the blanket passes to the rear of the machine,the coating swells in the water, and the swelling disintegrates the filmso thoroughly that by the time the blanket reaches the Washer l6 only acolored slime remains on the blanket which is easily removed by thewasher. The coating is of such a nature that it absorbs the solvent andthe color of resin ink, and clings on to these so tenaciously that theblanket itself remains permanently unaffected by the solvent or thecolor.

Once this apparatus has been set in operation, the only attendance whichit requires is to keep the supply tank filled with the coating slurryand at the end of the day release the wing nuts 8|- 82 which hold theslurry pan in place, wash out the pan and clean out the brush. '1

A dry, fresh printing surface is always presented at the printingstation, Excess color is carried away and stripped off from the blanketbefore the blanket cycle is complete, and since the coating itselfabsorbs both solvent and color to such an extent that it leaves theblanket free from attack, resin bonded inks can be used. All theadvantages of wash blanket printing are retained and the expense ofmaintaining back grays eliminated.

The coating compositions may vary greatly and may be based on suchwater-swellable substances as bentonite, caseinates, alpha protein,glue, albumins, etc. In all compositions, a film extender or loadingmaterial is helpful. This may be a substance such as whiting, infusorialearth, calcium carbonate or clay. Not only does the extender cheapen thecoating greatly and absorb the color and solvent, but, since thematerials are capillary active, they draw water into the film so rapidlythat a complete break-up of the film in the washing apparatus isassured.

In textile printing bentonite mixed with other clays provides the mosteconomical mix. I prefer to use equal parts (dry weight) of bentoniteand a well-refined rubber loading or paper coating clay and add 87 partsof water to produce a suspension having l2 by weight of suspendedsolids.

.The amount of the coating applied to the blanket I!) may be adjusted by(a) varying the depth of engraving or pattern of the depressions 45 onthe applicator roll 38, (b) adjustment of the spreader bar 56, (c)adjustment of the doctor blade 48.

In other applications, coating compositions of a precipitable nature arepreferred. For example, a composition of ammonium alginate, whiting andwater may be thinly coated on a waterproof draw sheet and coagulated bypassing under a licking roller supplied with a coagulant or precipitant,such, for example, as aluminum sulphate, calcium nitrate, etc., whichhas the efiect of converting the liquid composition into a hard, smooth,continuous film. After leaving the printing station, the whole film maybe stripped off the draw sheet by a well adjusted doctor blade. The easystripping of such coagulated films is surprising.

For simplicity of expression, the word ink used in the claims isintended to cover textile printing colors and dyes as well as oil, waterand organosol base inks used on paper.

I claim:

1. In a printing process, the steps which include forming a protectivecoating on the impression backing surface from a plastic substance,hardening the coating, passing the protected backing surface through theprinting station and absorbing excess ink thereon and removing thecoating from the backing.

2. In a. printing process, the steps which include forming on theimpression backing surface a protective coating composed of awater-swellable colloid and an extender, passing the protected backingsurface through the printing station and absorbing excess ink thereon,and removing the coating from colloid.

3. In a textile printing process, the steps which include forming on awash blanket a protective water-swellable coating, drying the coating,passing the coated blanket through the printing station and absorbingsurplus ink onthe coating, and swelling the coating to permit itsremoval.

4. In a textile printing process, the steps which include forming on awash blanket a protective coating formed from bentonite and an extender,drying the coating, passing the coated blanket through the printingstation and absorbing surblanket, means for washing and means for dryingsaid blanket, and means located aheadof the printing roll to apply aprotective coating on said blanket, and means to remove the coatingafter the blanket leaves the printing roll.

7. The process of printing which includes coating the impression backingsurface of a press with coagulable material, coagulating the material toform a protective coating, passing the coated backing surface throughthe printing station, whereby excess ink is deposited on said coating,and then stripping the coating from the backing.

8. The process of printing which includes coat ing the working surfaceof an impression cylinder of a press with ammonium alginate, coagulatingthe alginate, absorbing surplus ink on the alginate by passing thecoated working surface through the printing station and removing thealginate from the working surface.

9. In a, printing process, the steps which invclude forming a protectivecoating on the impression backing surface, hardening the coating,passing the coated backing surface through the printing station andabsorbing excess ink thereon and then removing the coating from thebacking surface.

WILLIAM C. ROSS.

the backing by swelling the

